To compare noise levels under real-life conditions we shot this scene with the Canon EOS 50D and EOS 40D within
a few moments of each other using each of their ISO settings.

We tested both Canon bodies with the same EF-S 18-200mm IS lens. The focal length of each lens was adjusted to deliver the same field of view and the aperture set to f8 for optimum sharpness.

The 50D's High ISO Noise Reduction was set to its default Standard, but the Auto Lighting Optimizer was Disabled for this test since it can artificially increase noise levels. The EOS 40D's High ISO NR was enabled; note this model does not apply its Auto Lighting Optimizer in the PASM and A-DEP modes.

The image above was taken with the Canon EOS 50D at a sensitivity of 100 ISO, using the EF-S 18-200mm IS kit lens at 20mm f8; the original Large Fine JPEG file measured 3.92MB. The crops are taken from the centre and presented at 100%. The 40D crops show a larger area due to its lower resolution. Note the 40D required +0.3 EV of exposure compensation to match the exposure of the 50D here.

When the EOS 50D was announced, Canon made bold claims about how gapless micro-lenses on the sensor would allow the new camera to match the noise levels of the earlier 40D. That's quite a claim considering the 50% increase in total pixels, but judging from the results below,
there's certainly some truth in it.

At 100 and 200 ISO, both cameras deliver silky smooth output. At 400 ISO, pixel peepers will notice a very faint smattering of noise in the background, but again its similar on both cameras. Between 800 and 3200 ISO, both cameras exhibit greater increases in visible noise artefacts, although some may find the new 50D slightly smoother. This would however appear to be down to greater noise reduction on the 50D by default - if you check our Noise Reduction page, the samples with the Low setting are closer to the 40D.

The 50D then bravely goes on to offer 6400 and 12800 ISO modes, but both suffer from significantly reduced image quality. Noise levels are considerably greater, there's visible horizontal banding, and the 12800 ISO sample additionally has more than its fair share of red hot pixels. So we'd avoid the top two sensitivities on the 50D unless you really have no other choice.

But between 100 and 3200 ISO, the EOS 50D really does deliver very similar noise levels to the earlier 40D at a pixel level. This is impressive given the significant boost in total pixels and remember if you're reproducing 40D and 50D images at the same size, the 50D's noise artefacts will appear smaller. It also proves the 50D's greater sensor efficiency in practice, although now the micro-lenses are gapless, the engineers are running out of options to further boost resolutions without compromising noise given the APS-C real-estate.